Rheostat



(No Model.)

T. J. FAY.

RHEOSTAT.

No. 556,408. Patented Mar. 17, 1.896.

INVENTOR WITNESSES ATT NEY UNITED STATES "PATENT OFFICE.

THOMAS J. FAY, OF BROOKLYN, NEV YORK, ASSIGNOR-TO THE C. & O. ELECTRICCOMPANY, OF NEV JERSEY.

RH EOSTAT.

SPECIFICATION forming part of Letters Patent No. 556,408, dated March17, 1896.

Application filed December 19, 1895. Serial No. 572,649. (No model.)

To aZZ whom it may concern.-

Be it known that I, THOMAS J. FAY, a citizen of the United States,residing at Brooklyn, in the county of Kings and State of New York, haveinvented certain new and useful Improvements in Rheostats, of which thefollowing is a full, clear, and exact description.

This invention relates to rheostats intended for starting and regulatingelectric motors.

The object of the invention is, first, to provide an apparatus whichwill automatically protect the motor against burning out or seriousinjury due to overloading; second, to provide means for enabling arheostat to carry more current than it would naturally carry; third, tocheapen and improve the details of construction of rheostats, while atthe same time improving their operation.

The invention consists of constructions an d combinations hereinafterdescribed and particularly pointed out in the claims.

In the accompanying drawings, Figure l is a face view of my improvedrheostat. Fig. 2 is a section of the face-plate of the rheostat, takenon line 00 a: of Fig. 1 and showing also certain circuits with which therheostat is connected. Fig. 3 is a sectional view of the casinginclosing the rheostat and means for ventilating it.

A represents the face-plate of the rheostat. It is of insulating1naterialsuch as slate, as usual-and upon it are secured a series ofmetallic contact-pieces a, arranged in the arc of a circle andconstituting the terminals of a series of resistance-coils of ordinarycharacter, which are supposed to be located in a frame at the rear ofthe face-plate. Concentric with this row of contact-pieces is acontinuous metallic strip a. At the center of these arcs a handle B ispivoted. This handle carries at its forward end a rectangular frame 6,in which is placed a block of carbon Z), adapted to connect the are awith the contact-pieces in the arc to. This block of carbon is looselyplaced in the end of the handle, but the pressure with which it bearsupon the contact-pieces is regulated by a spring b which is fixed at oneend to the handle at the point 6 and its tension adjusted by the screwN. The contact-pieces in the are a are of peculiar shape, their adjacentedges or sides being zigzagged-that is, one side forms a convex obtuseangle and the other a concave obtuse angle, the projection of onefitting into the cavity of the other. By this formation I am able toplace the pieces comparatively far apart to prevent bridging by carbondust or arcing and at the same time maintain a large surface of contactbetween the pieces and the block of carbon as the latter moves from onepoint to another, the contact with one being made before it is brokenwith the other.

At each end of the throw of the lever is placed a stop 0 and d. When thelever is against the stop c all resistance is cut out and when againstthe stop cl the circuit is broken. The stop 0 and the post 011 which thelever turns constitute the poles of. a horseshoe electromagnet e,connected together by the yoke e. The coils of this magnet are shown at6 The rheostat-lever is made of magnetic material, so that when thelever is against the stop 0 the magnetic circuit is completed and anattraction will exist between the stop and the lever.

Surrounding the post of the lever is a tor sion-springf, one end beingfixed to the lever and the other passing through a slit in stud f. Thetension of this spring may be regulated by means of screws f Thetendency of the spring is to keep the lever in contact with the stop d.

The motor which the rheostat controls is represented at M. It is ashunt-wound motor, the field-circuit of which includes one of the coilsof magnet e, the other coil being in the armature-circuit of the motorand wound in opposition to the first coil. The magnetism induced by thecoil in the fieldcircuit is in opposition to and stronger than the pullof spring f. hen the motor is running with all the resistance out-thatis, when the lever is against stop cthe lever is held in that positionby the magnetic attraction.

In starting the motor the lever is gradually moved from its positionagainst stop cl to the stop 0, where the motor normally would run atfull speed; but if the motor should be overloaded, or for any reason didnot run up to its full speed, the armature would then draw more currentthan it should and the excess would be felt in magnet e, and, acting inconjunction with the spring f, would overcome the magnetism induced bythe field-circuit and release the lever, allowing it to fly back to stop(Z under the action of the spring, thus saving the motor, the rheostat,and the fuses from possible injury.

My invention, broadly considered, involves a magnet energized by twocircuits opposed to each other, and one carrying a current of constantstrength and the other one of variable strength. As such, the inventionis not limited to the shunt and armature circuits of a motor.

Ordinary starting-rheostats are usually designed to carry their heaviestcurrents but a short time, and if subjected to such currents for aconsiderable period will burn out. I propose to divide the totalresistance of the rheostat into two parts, making the conductor of anelectromotor one of the parts and utilizing the power of such motor tocreate a current of air for cooling the other part. This idea is carriedout in the following manner: An ordinary fan-1notor is placed in a boxit, having an open front 1' and connnunicating with the chambercontaining the resistancecoils of the rheostat through a passage). Themotor carries a fan 7a, which draws air into the box and forces itthrough the rheostat. In this way the temperature of the wires ismaintained at a low point constantly, and they will therefore carryheavier currents than they otherwise would.

This motor is in the armature-circuit with the regular rheostat andoperates in conjunction therewith, and is controlled by the switch onthe face of the rheostat. The current which it consumes is therefore putto use instead of being wasted, as in the coils of the other portion ofthe resistance.

IIaving fully described my invention, I claim- 1. In a rheostat orswitch, the combination of a controlling-lever, an eleetromagnet thelever being pivoted to one of the poles of the magnet, a spring arrangedto swing the lever on its pivot, the magnet being included in twocircuits adapted to oppositely magnetize its core; substantially asdescribed.

2. The combination with a shunt-wound electric motor of a rheostattherefor, a controlling-lever for the rheostat, an electromagnet, thelever being pivoted to one of the poles of the magnet, a spring arrangedto swin g the lever on its pivot, the magnet being wound with twoopposing coils located ro spectively in the lield and armature circuitsof the motor; substantially as and for the purpose set forth.

3. In a rheostat or switch, the combination of a controlling-lever, anelectromagnet, the lever being pivoted to one of the poles of themagnet, a spring, whose tension may be adjusted, arranged to swing thelever on its pivot, the magnet being included in two circuits adapted tooppositely magnetize its core; substantially as described.

I. In a rheostat or switch, the combination of a controlling-lever, anelectromagnet the lever being pivoted to one of the poles of the magnet,a spring, arranged to swing the lever on its pivot, the magnet beingincluded in two circuits adapted to oppositely magnetize its core, oneof said circuits carrying a constant current and the other a variablecurrent; substantially as described.

5. In a rheostat or switch, the combination of a controlling-lever, aneleetromagnet, the lever being pivoted to one of the poles of themagnet, the magnet being included in two circuits adapted to oppositelymagnctize its core, one of said circuits carrying a constant current andthe other a variable current; substantially as described.

6. The combination of a rheostat, a box or chamber connected therewith,an electric fan located in said box or chamber and suitable openingsinto the box and from the box into the rheostat, whereby a blast of airmay be sent through the rheostat, substantially as described.

7. The combination of an ordinary rheostat and an electromotor, theconductors of the motor forming a part of the resistance medium of therheostat; substantially as described.

S. The combination of an ordinary rheostat and an electromotor, theconductors of the motor forming a part of the resistance medium of therheostat and means whereby the motor may be used to ventilate the otherportion of the resistance medium; substantially as described.

In testimony whereof I subscribe my sig nature in presence of twowitnesses.

THOMAS J. FAY. \Vitnesses:

W M. A. ROSENBAUM', FRANK S. OBER.

